Steel-coated board



July 2, 1929. H, C, HARVEY I 1,719,607

STEEL COATED BOARD Filed Jan. 1l, 1928 WITNESS l INVENTOR ATTORNEYS Patented' July 2, 1929.

UNITED STATES I 1,719,607 `PA'rElSrrf oFFlcE.

HAROLD C. HARVEY, OF TREN TON, NEW JERSEY, ASSIGNOR TO THE .GASOTILU MILL- BOARD COMPANY, F EWING TOWNSHIP, NEW JERSEY, A.

JERSEY.

CORPORATION 0F NEW STEEL-COATED BOARD.

Application led January 11, 1928. Serial No. 246,067.

My invention relates to aboard, oneside of which has applied thereto, by suitable cementing means, a sheet of enameledsteel This kind of board ma bensed for many purposes, for instance, t e lining of railroad cars, dairies, bathrooms, kitchens, pant-ries, etc., and has the ladvantage of being sanitary, easily cleaned, lire-resisting and not liable to be damaged by any but hard blows.

Enameled sheet steel is well known in the art of steel treatment. As is known to those skilled in such art, steels of a special ty are used for this purpose, which are subjected to a stretching operation and a pre-` liminary surfacing operation `(ground coating).` The enamel powder is then placed upon the steel so treated and fused thereon in a kiln or furnace heated to aY temperature suicient for this purpose, usually in the neighborhood of 2500o F.- When the steel is i thereafter cooled it assumes a distorted form, unless it has been reinforced in some manner. Such steel, when subjected (prior to enameling) to the pressing operation which forms it into utensils of various kinds (pans, vtable tops, etc), is capable of assuming and maintaining such forms as the presses may v give to it, in part, at least, by reason of reinforcement by the angles and other supporting shapes formed by the pressing. If, however, the steelv sheet is of a substantial size and is to be employed in a iat form only, there is no practicable process known to the art by which such steel can bemade to assume and maintain such form without the aid of additional material. Such steel will, of course, when held flat, always tend to assume the shape which it had immediately after the completion of the cooling. I am speaking, of course, only of a. steel sheet of such thickness and size asv will,- after enameling and subsequent cooling, assume without thev application of a bending process a substantially curved form.' Comparativer 4e ly small sheets even of relatively thin'steel,

will not be distorted to-a substantial degree during the 'enameling process, and sheets of larger size, but thicker material, will also not be distorted to any substantial degree. My referred size of sheet is, for inst-ance, ten et long, ,four feet Wide and of a thickness indicated by gauges 18 to ,10. It isr to' i this type of sheet that I refer in my claims asA enameled steel whichnormally assumesa.

curved shape. If such sheet is mounted on a backing ot weaker material this tendency will cause or tend to cause such backing to assume a form which, when looked at from the armored side, will be convex.

My invention in its preferred form contemplates the application of la sheet of enam-v eled steel by a suitable cementing means to 1 a backing of material which is affected by atmospheric moisture and is capable of being .distorted ythereby to a substantial extent.

My backing may consist, for instance, of pulp board or breboard, preferably pulp board which may be made by running a" mixture of pulp and water, to which a binder mayl have been added, into a mold, removing the majority of the water by pressure, remo'v ing the remainder of the Water by the application of heat, preferably in-a suitably constructed drier (see United States-'Letters Patent No. 971,936 dated October 4*, '1910 land No. 1,272,566dated July 16, 1918). 'When libre board and particularly a-pulp board such as hereinbe ore specifically described,"

is subjected to moisture equally on -both sides, fit tends to stretch with only a com' paratively 4slight tendency to distortion. If

it is subjected to moisture on, oneside'only, the exposed side tends to expand and will therefore tend to give Athe board a concavoconvex form, the exposed side forming the convex side.y Instead of a pulp board I may use any other suitable material backing, for instance,wood.

As already explained, non-reinforced'l draw, ortend to draw, the backing into con- ,cavo-convex form, the convex side being the one to which the steel is attached. If, now,

the expoed side of the Backingv be humidi-v fied, 'such' backing will tend to be drawn into concavo-convex form but with the eX- posed side forming the convex side and will thus tend to drawin a direction opposite to .that in which it is pulled by the steel. vIf

the backing is of .such a nature and of such proportions that the addition of la suitable Cil which it usually comes from the drier.

amount of moisture to this exposed side will cause it to neutralize the pull of the steel sheet, a flat panel will result, whereas if conditions are such that the pull of the steel is more than overcome, the panel will be concavo-convex with the steel on the concave side. Again, if the pull of the steel is not entirely overcome, the panel will remain concavo-convex but not so much as before the application of the moisture.

In the accompanying drawings, Fig. 1 shows a cross-section of a backing, having applied thereto a layer of cementing material and a cross-section of a sheet of enameled steel also provided with a layer of cementing material, and ready to be stretched flat and pressed upon the backing. Fig. 2 shows a cross-section of the assembled board before moisture has been applied to the exposed side of the backing only and in which the steel is strong enough to distort the backing. Fig. 3 shows the completed board after a suitable amount of moisture has been applied to the exposed side of the backing, after the panel has been assembled.

In the figures a represents the backing, b the cement on the backing, c the cement on the steel, d the steel and e the enamel coating. The cement may be of any suitable type and is preferably a rubber cement.

I shall now describe an example of the practice of my invention for use in making a composite panel having a substantially Hat form. I employ a sheet of steel and a backing having such relative strength that the steel will actually distort the backing when the latter is in the bone-dry conditionI1 iln e backing, when subjected to the average degree of atmospheric moisture at the place at which the panel is to be used, must be capable of pulling the steel sheet to flat forml or to almost fiat form.- I then apply the sheet to the backing by means of the cement described, `while 'such backing is bone-dry. I then exposethe composite panels to conditions of average atmospheric moisture to be met at the point of use. trying out the panel at the point, of use o-r by subjecting it at the factory' to air-conditioned apparatus in which such average conditions are reproduced. If I find upon such test that the panel will be pulled into and remain substantially in' a Hat form, I manufacture the panels for use at such point by applying steel to bone-dry backing. If, on

the other hand, I find that the backing pulls the steel from the convex form into the concave form, I make another panel using a backing to which a slight amount of moisture has been added by subjecting the same on both sides to a humidifying process and repeat the test, continuing, if necessary, with increased amounts of 'moisture in the' back-4 ing before attaching until a fiat paneliisl I may do this either by.

produced. By this trial and error method strain set up by the additional moisture applied to the exposed side under average atmospheric conditions at the point of use, will be just sutlicient to draw the panel into straight form or into almost straight form. In practice I have found that it is always advisable to have some moisture in the backing before applying the steel thereto because I contemplate the use of as thin a sheet of steel as feasible and as strong a backing as commercially feasible. By increasing the moisture content of the backing before the steel is applied, I diminish the amount of additional moisture taken from the atmosphere by the panel and therefore diminish the tendency of the panel to assume a concave form. I prefer to have the completed panel, after exposure to such average atmospheric conditions, slightly convex, considered from the steel side, because a temporary excess of moisture in the atmosphere will then do no more than draw the panel quite flat and a temporary deficiency will tend to draw'it into slightly more convex form. I have found that the human eye is disturbed by a panel which is concave asa whole or in part or parts (for instance, when applied to the strainers of a delivery wagon body) whereas it is not offended vby convexity.

Of course, if for some special reason I desire to have the panel either permanently substantially convex or permanently substantially concave, I modify the various conditions so as to obtain this end without, however, departing from the principle of my invention. The preferred form of my invention, wherein a sheet of enameled steel is cemented to a relatively thin and flexible backing composed of hygroscopic material, is important because for the manufactureof armored panels on alarge scale it is desirable .to have a backing of as'light weight as possible.

If the conditions at the point of use are l degree, and perhaps entirely, bycompressing certain portions ofthe steel prior to the enameling processso as to form strengthening ribs-for instance, by compressing the steel along the lines which will form square or lozenge patterns. This discovery will form the subject-mattersof a separate application for Letters Paten't.\` To the extent to diminishedfby this method, or possibly by and pressure sufficiently high to fuse the i binder and to compact the backing, but not more careful methods of supportin the steel in the furnace, during the ename in ess, or possibly tothe subjection of t e steel to lower temperatures during such process,

the initial moisture content of my backing4 will have to be increased, .other things being equal. If the enameled steel after cooling should be substantially flat and if substantially no tendency to assume a curved shape exists, then my process will obviously have to be so modified, that is to say, so restricted that the original moisture content of the backing is determined only by'the conditions to be met at the point of use without taking vinto consideration the necessity of overcoming the tendency of the panel as a whole to assume a convex form. In other words, the more nearly the steel tends to remain in a flat form, the more nearly the original moisture content of the backing should be such that no additional moisture is absorbable thereby at the point of use.

If the pulp board used by me contains a fusible binder, I prefer not to subject the backing to the usual heat and pressure (see, for instance, United States Letters Patent No.' 1,598,260) before cementing the steel thereto, but to' perform such o eration when I press the steel thereon; in ot er words, instead of forming an assembled panel by pressure only, I form it by. applying heat so high as to. drive away an a preciable proportion of the moisture in t e board. Of course, I may allow, when applying mois ture to the backing in the first place, for loss of moisture during such compressing y operation by adding an excess of moisture a suitable cement to a backing approximately equal to that which would be evaporated during thepressing operation. I

also permit the presslto cool, before releasing pressure, to an extent sufhcient to con` dense any steam whichmay have formed within the board. In practice, however, I find it unnecessary to subject the boardeto as high a. degree of pressure as might be thought essential and therefore do not expose it to the high temperature long enough to have steam form as the sheet steel will supply the strength which would otherwise have to be supplied by longer subjection to heat and pressure.- v

-I may attach the enameled steelrsheetby which is strong enough to hold it so that the composite panel will not/be distorted by the steel.l Such backing may comprise a wooden board, or a pulp or fibre board, or a platser board, or an asbestos board, of such strength as to be capable of resistin the bending stresses in the enameled steel acing, or it'may comprise a relatively thin board suitably reinrial.

forced to resist bending.v All of the foregoing backing materials, and many equivalents that may suggest themselves as substitutes therefor, are included in my claims by the expression fibrous hygroscopic mate- It is ofcourse understood that when an exceedingly porous type of backing is used, a coatin of varnish or the like may be found desirable to prevent transfer of moistilre between the backing and the atmosere. p When I refer in my claims to steel I desire it to be understood that such term in-y cludes not only steel but any other metallic material, such as iron, which assumes a curved form when cooled after enameling, Whether or not it has been subjected to the particular treatment of stretching and ground coating hereinabove described. It is, of course, to be understood that the enamel powder used must be of such anature, and applied in such a manner, that the baked enamel'is capable of being flexed with the steel without crazing.. Such enamel, and the method of applying it in such manneri, are well known to manufacturers of enameled steel.

I claim: y

1. In a composite panel a facing of enam` eled sheet steel, a backing of fibrous hygroscopic material attached thereto, the 'internal structure and stresses of said facing being such as to cause it to assume a distorted form in the absence of any counteracting external infiuence, and moisture distributed substantially throughout the backing in such predetermined quantity that the internal stresses developed in the backing are sufficient` to substantially counteract-the internal stresses of the facing and thereby prevent distortion thereof.

2. In a composite panel a facing of enameled sheet steel, a backing of fibrous hygroscopic material cemented thereto, the internal structure and stresses of'said facing being' ,suchN as to cause it to assume a curved form in the absence of any counteracting external infiuence, the said backing beingweaker than the facing so as to be' capable of being distorted thereby, and moisture uniformly distributed in the outermost side Yof the backing in such predetermined quantity as to cause said side to expand and draw upon the facing to limit the curvature thereof.

3. The method of making a composite panel, consisting in selecting` a facing of enameled steel,V which normally assumes a curved shape, attaching thereto a backingpf fibrous hygroscopic material, which backing is weaker than such facing so as to be capf moisture to the-portion' of the .backing whic lthefac'ing sucient in quantity to cause the 'lies immediately behind the side opposite" backing to draw the facing and thus alter the curvature of the panel.

4. The method of making a composite panel consisting in selecting a facing Aof enameled steel, which has a normal tendency to assume a distorted shape, attaching thereto a backing of fibrous hygroscopic material, which backing is weaker than such facing so as to be capable of being distorted there by, adding moisture to the backing, before it is attached to the facing, distributing said moisture substantially throughout the backing in such quantity that after the panel has been assembled such backing, at the point of use, will absorb no more moisture from the atmosphere than is sulicient to cause it to draw the panel to a-predetermined shape.

5. The method of making a composite panel from a facing of enameled steel, which normally assumes a curved shape, consisting in ccmenting thereto a backing of fibrous vhygroscopic material, which backing is weaker than such facing so as to be capable of being distorted thereby, adding to the backing, before it is attached to the facing, moisture in substantially uniform distribution throughout the backing in such quantit 'that after the panel has been assemble such backing, at the point of use, Will absorb no more moisture from the atmosphere than is sufficient to cause it to draw the panel to substantially fiat shape.

HAROLD C. HARVEY. 

